Joint exercises still require agreement on the lessons

Would more joint Navy and Air Ministry exercises in the 1930s have improved war preparation?

They would help to a degree, though disagreement over the results could prevent the lessons from being applied.

More interwar joint exercises could expose operational problems and improve war preparation to a degree. Their value would depend on the Navy and Air Ministry agreeing about what the results meant and acting on them. The exercise itself could produce evidence without resolving the institutional dispute over its interpretation.